1. Filed of the Invention
The present invention relates to a voltage detecting device, particularly to a voltage detecting device for detecting each voltage of each block of a plurality of blocks divided from a battery unit formed with a plurality of unit cells, which is secondary battery type, connected in series to each other.
2. Description of the Related Art
Recently, a hybrid electric vehicle (HEV), which travels by using both an engine and an electric motor, has been widely used. The HEV has a low voltage battery of 12 volts for starting the engine, and a high voltage battery for driving the electric motor. The high voltage battery is formed with a plurality of unit-cells, connected in series, such as a nickel-metal hydride secondary battery or a lithium secondary battery.
The above high voltage battery including battery packs is divided into a plurality of blocks, and provides respective blocks with a voltage detection IC (Integrated Circuit), for example, patent documents 1 and 2. The respective voltage detection IC detects both terminals of unit cells, and transmits the detected the detected result to a main microcomputer (control device) which controls the high voltage battery. The plurality of voltage detection ICs is connected to the main microcomputer through a common communication line so as to reduce lines or terminals.
In the above described multiple voltage detection ICs, an address is set so as to give and receive a signal between the main microcomputer and a plurality of voltage detection ICs through the common communication line. Thereafter, each voltage detection IC attaches a self-address to the detected result, and transmits. Thereby, the main microcomputer can distinguish the unit cell of the block by the detected result which is received.
As a method setting this address, a method for appending an address selecting switch to an external terminal of the voltage detection IC and for selecting an address depending on ON/OFF of the address selecting switch is known. However, the above conventional method should provide the voltage detection IC with a special external terminal so as to select the address. Furthermore, since a lot of external terminals are required by the number of address, it causes an increasing manufacturing cost.
Alternatively, another method for using power sources of all voltage detection ICs as a common power source, transmitting an address signal to a power source line and setting the address of respective voltage detection IC is known. However, in the above mentioned conventional method, it is necessary to equalize an electrical potential of power source in the voltage detection IC. Thereby, when the electrical potential of power source in the respective voltage detection IC is not equalized, the conventional method can not be used with a voltage detecting device.
Patent Documents 1:    Japan published patent application 2006-42591
Patent Documents 2:    Japan published patent application 2007-187649